Oriented Strand Board (OSB) is an engineered structural-use panel typically manufactured from thin wood strands bonded together with resin under heat and pressure, and it is used extensively for roof, wall, and floor sheathing in residential and commercial construction.
One drawback associated with known oriented strand boards (OSB) is that they are susceptible to decomposition by fungus. The problem is especially pronounced in the south eastern corridor of the United States (e.g., Florida and Louisiana). Several fungicides have been used in the pressure treatment of wood. The resulting pressure treated wood products may be temporarily resistant to fungus. However, many of these compounds are either extremely poisonous or are not suitable in the OSB manufacturing process.
Specifically, arsenic containing compounds, borates, and halogenated compounds (e.g., chromated copper arsenate (CCA), ammoniacal copper quat (ACQ), ammoniacal copper zinc arsenate (ACZA), creosote, and pentachlorophenol) have been used with limited success in the pressure treated wood industry. Arsenic is poisonous and its use has been criticized by several environmental groups.
The use of many known fungicides to produce oriented strand boards results in an oriented strand board with unacceptable physical properties. For example, many fungicides may undergo physical decomposition during the extreme conditions (e.g., temperature and pressure) typically experienced in the pressing stage (i.e., the step in which the resin is cured). As such, the resulting oriented strand board may not even be resistant to fungal infections.
The fungicide may not be chemically compatible with the resin. Moreover, the fungicide may lose its effectiveness over an extended period of time (e.g., about 25 years) and under normal weather conditions (e.g., rain, snow, heat, exposure to UV light, etc.). For example, the fungicide may leach out of the OSB over an extended period of time and under normal weather conditions.
Published PCT Application WO 03/062345 A2 discloses suitable antifungal formulations and methods of using these formulations to treat various substrates. This published PCT application, however, does not describe with sufficient detail, or provide any guidance on how to manufacture processed wood products (e.g., OSB or plywood) employing such antifungal formulations. Such processed wood products employ in the processes various substances (e.g., resins, waxes, etc.) as well as conditions (e.g., elevated temperatures and elevated pressures) that must be compatible with the antifungal formulations described therein to effectively provide a wood product that is antifungal.
As such, what is needed is a fungal resistant OSB; and processes for making the same. The fungal resistant OSB should include a fungicide that retains its effectiveness (i.e., antifungal properties) during the manufacturing of the OSB. The fungal resistant OSB should include an fungicide that retains its effectiveness over the extended periods of time typically encountered with the lifespan of the oriented strand board (e.g., up to about 25 years, up to about 50 years, or up to about 100 years).
During the manufacture and over the lifespan of the OSB, the fungicide should remain stable in the presence of the resin. The fungicide will preferably be inexpensive, easy to manufacture, convenient to use, environmentally safe, and/or chemically stable.